mirror of OpenBSD xenocara tree
github.com/openbsd/xenocara
openbsd
1/*
2 * Copyright © 2022 Advanced Micro Devices, Inc.
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 */
23
24#include "nir.h"
25#include "nir_builder.h"
26#include "nir_builtin_builder.h"
27
28typedef struct {
29 bool set_barycentrics;
30 nir_intrinsic_instr *found_baryc;
31} lower_point_smooth_state;
32
33static nir_intrinsic_instr *
34find_any_used_barycentrics(nir_function_impl *impl)
35{
36 nir_foreach_block(block, impl) {
37 nir_foreach_instr(instr, block) {
38 if (instr->type == nir_instr_type_intrinsic) {
39 nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
40 if (intr->intrinsic == nir_intrinsic_load_barycentric_pixel ||
41 intr->intrinsic == nir_intrinsic_load_barycentric_centroid ||
42 intr->intrinsic == nir_intrinsic_load_barycentric_sample)
43 return intr;
44 }
45 }
46 }
47
48 return NULL;
49}
50
51/**
52 * This NIR lowers pass for point smoothing by modifying the alpha value of
53 * fragment outputs using the distance from the center of the point.
54 * Anti-aliased points get rounded with respect to their radius.
55 */
56
57static bool
58lower_point_smooth(nir_builder *b, nir_intrinsic_instr *intr, void *state)
59{
60 lower_point_smooth_state *s = (lower_point_smooth_state *)state;
61
62 if (intr->intrinsic != nir_intrinsic_store_output &&
63 intr->intrinsic != nir_intrinsic_store_deref)
64 return false;
65
66 int out_src_idx;
67 if (intr->intrinsic == nir_intrinsic_store_output) {
68 int location = nir_intrinsic_io_semantics(intr).location;
69 if ((location != FRAG_RESULT_COLOR && location < FRAG_RESULT_DATA0) ||
70 nir_intrinsic_src_type(intr) != nir_type_float32)
71 return false;
72 out_src_idx = 0;
73 } else {
74 nir_variable *var = nir_intrinsic_get_var(intr, 0);
75 if ((var->data.location != FRAG_RESULT_COLOR &&
76 var->data.location < FRAG_RESULT_DATA0) ||
77 glsl_get_base_type(var->type) != GLSL_TYPE_FLOAT)
78 return false;
79 out_src_idx = 1;
80 }
81
82 assert(intr->num_components == 4);
83
84 b->cursor = nir_before_instr(&intr->instr);
85
86 /* Determine the barycentric coordinates. */
87 nir_def *baryc;
88
89 if (s->set_barycentrics) {
90 baryc = nir_load_barycentric_pixel(b, 32,
91 .interp_mode = INTERP_MODE_SMOOTH);
92
93 /* Since point interpolation mostly doesn't care about which barycentrics
94 * are used, use any that are used by the shader. This is an optimization
95 * for hw that is faster if only one set of barycentrics is used.
96 */
97 if (s->found_baryc) {
98 nir_intrinsic_instr *baryc_intr =
99 nir_instr_as_intrinsic(baryc->parent_instr);
100
101 /* Overwrite the intrinsic we just created. */
102 baryc_intr->intrinsic = s->found_baryc->intrinsic;
103 nir_intrinsic_set_interp_mode(baryc_intr,
104 nir_intrinsic_interp_mode(s->found_baryc));
105 }
106 } else {
107 baryc = nir_undef(b, 2, 32);
108 }
109
110 nir_def *coord = nir_load_point_coord_maybe_flipped(b, baryc);
111
112 /* point_size = 1.0 / dFdx(gl_PointCoord.x); */
113 nir_def *point_size = nir_frcp(b, nir_ddx(b, nir_channel(b, coord, 0)));
114
115 /* radius = point_size * 0.5 */
116 nir_def *radius = nir_fmul_imm(b, point_size, 0.5);
117
118 /**
119 * Compute the distance of point from centre
120 * distance = √ (x - 0.5)^2 + (y - 0.5)^2
121 */
122 nir_def *distance = nir_fast_distance(b, coord,
123 nir_imm_vec2(b, 0.5, 0.5));
124 distance = nir_fmul(b, distance, point_size);
125
126 /* alpha = min(max(radius - distance, 0.0), 1.0) */
127 nir_def *coverage = nir_fsat(b, nir_fsub(b, radius, distance));
128
129 /* Discard fragments that are not covered by the point */
130 nir_discard_if(b, nir_feq_imm(b, coverage, 0.0f));
131
132 /* Write out the fragment color*vec4(1, 1, 1, coverage)*/
133 nir_def *one = nir_imm_float(b, 1.0f);
134 nir_def *new_val = nir_fmul(b, nir_vec4(b, one, one, one, coverage),
135 intr->src[out_src_idx].ssa);
136 nir_src_rewrite(&intr->src[out_src_idx], new_val);
137
138 return true;
139}
140
141bool
142nir_lower_point_smooth(nir_shader *shader, bool set_barycentrics)
143{
144 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
145 nir_function_impl *impl = nir_shader_get_entrypoint(shader);
146
147 lower_point_smooth_state state = {
148 .set_barycentrics = set_barycentrics,
149 .found_baryc = set_barycentrics ? find_any_used_barycentrics(impl) : NULL,
150 };
151
152 return nir_shader_intrinsics_pass(shader, lower_point_smooth,
153 nir_metadata_loop_analysis |
154 nir_metadata_block_index |
155 nir_metadata_dominance,
156 &state);
157}